var modifyB = document.getElementById('modifyB');
modifyB.addEventListener('click', function() {
	document.getElementById('buttoms').style.display = "";

	var td = document.getElementsByTagName('td');
	for (var i = 0, c = td.length; i < c; i++) {
		if (i % 2 == 1) {
			td[i].style.display = "";
		}
	}
}, false);

